Apple/Mac floppy questions

Tony Duell ard at p850ug1.demon.co.uk
Mon Aug 2 14:49:18 CDT 2010


> 
> Tony wrote:
> >> One thing to watch for are the little 20-way Apple ribbon cables that
> >> link these drives to the mainboard. They are not what they seem -- in
> >> particlar 1 ro 2 wries are not wires at all, but solid plastic, so those
> >> pins of the connectors are not linked. If they are, then all sorts of odd
> >> things happen (Eject motor runs continuously???)
> >>
> >> I beelive there are at least 2 versions of the calbe (for double sided
> >> and high density drives>?, with different coloured pin 1 tracers. A Mac
> >> enthusiast may know more.
> >>      
> Jeff wrote:
> > I don't remember all the details.  I do remember that there is a cable
> > with a yellow stripe on pin 1 and another version of the cable with a red
> > stripe.  If you install the wrong cable (can't remember whether it's red
> > for yellow or yellow for red) the eject motor does indeed run
> > continuously.
> >
> > It doesn't seem to damage the drive; I never let it run more than a few
> > seconds.  So it's easy enough to identify and correct.
> >    
> There's a dedicated eject signal on the 800K and FDHD that will cause 
> the drive to eject.  IIRC it is active low, and replaced a ground.  The 

I thought it was actually a -5V line on the computer end of the cable, 
but the schematics are not to hand...

> internal drive connectors in the Mac are not wired for that eject signal.
> 
> The dedicated eject signal is probably used in the external drive 
> enclosure for the eject button.  Software can tell the drive to disable 
> the manual eject and poll the button instead.  Or something like that.

IRIC, this eject pin is wired directly to the eject motor driver circuit, 
it doesn't go via any logic (e.g. the digital ASIC) so I don't see how 
software could do this unless there was more external logic involved 
(which is entirely possible, of course).

I thought the cables were different between the 800K and FDHD drives, but 
I might well be wrong. I don't have much experience with Macs...

-tony



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